Agricultural Soil Classification

Soil Orders and Suborders

• The 11 soil orders refer to the environment where the soils are found. Aridsols, for example, are found in arid climates, and Mollisols are found in grassy environments. The suborders usually indicate the conditions under which the soil was created. For example, a suborder that begins with the letters "aqu" probably was formed by water, and "cry" was formed by ice. These are usually very general descriptions, and a gardener is likely to already be familiar with the environment where the soil is located.

Great Groups and Subgroups

• Great groups and subgroups further differentiate soil groups. Great groups describe more specifically the elements that formed the soil. For example, soil may have been formed from leaves. Subgroups are even more specific, and often refer to levels of moisture control. Knowing a soil's construction or moisture control gives us clues about what can be planted successfully in a garden, or what we will have to add to amend the soil. Soils formed from leaves are likely to be more acidic, for example, so choose plants that tolerate acidic soils, or apply a soil sweetener like lime.

Families and Series

• Families are often more definitive with regard to agricultural use. Series usually indicate where the soil was found -- for example, Portland, Oregon or San Joaquin, California. While soils are not usually classified to this level, it is perhaps the most important aspect when considering a garden. A loamy soil, for instance, holds more water, and a sandy soil drains better. Also, knowing what soils are characteristic to your area helps you meet or overcome soil-related gardening challenges that may be common for the region.

Short History Of The Classification System

• Soil classification is not a new science. Some of the earliest attempts at classifying soils were found in China -- where they were classified according to their productivity. Soils were classified in the 1800s according to texture; for example, a soil may be gravelly or sandy. As late as 1975, soil classification was still developing, and soil origin and productivity were both considered. When investigating your garden's soil classification, keep in mind that different types of classification exists.